1179.2 Uncertainty quantification in soi

Researchers: Jonathan Sanderman (Associated with)

Brief description A long-standing agroecological dichotomy states there is a tradeoff between storing carbon as soil organic matter (SOM) and the nutrient and energy benefit provided during its decomposition. Here we report on results from the Waite Permanent Rotation Trials which demonstrate that management which return more carbon to the soil not only leads to greater carbon stocks, but also increases the rate of carbon cycling and thus nutrient provision from SOM relative to a low carbon return management. After >40 years under consistent management, topsoil carbon stocks ranged from 14 to 34 Mg C ha-1 and were linearly related to the mean productivity of each treatment. Measurements of organic matter composition demonstrated increasing amounts of plant- and microbially-derived SOM along the productivity gradient. Radiocarbon data indicated overall SOM turnover time decreased from 40 to 13 years with increasing productivity. Similarly, the half-life of synthetic root exudates decreased from 30.4 to 21.5 hours with increasing productivity indicating accelerated microbial activity. These findings contradict a core tenant of many soil carbon models and suggest that there is a direct feedback between accelerated biological activity and carbon cycling rates.